The present invention relates to a busbar structure which is attached to an electric motor and provided with busbars which function as relay members for relaying electrical connection between the electric motor and a control circuit and so on as an external circuit, a method of producing the busbar structure, and the electric motor having the busbar structure.
An electric motor provided with a stator core around which a coil is wound interposing an insulator has been heretofore known. Among the electric motors of this type, there is an electric motor provided with a busbar integrated type insulator which is formed by integrating an insulator for insulating the stator core from the coil and the busbars as the relay members for relaying electrical connection between the coil and an external control circuit and so on (Reference should be made to JP-A-2005-341640). In this case, the busbar is a sheet member formed of metallic material such as pure copper plated with tin which is cut into a determined shape and then, folded in a determined direction.
Generally, production of the busbar integrated type insulator as described above is conducted by in-mold molding, which is a kind of injection molding, in which a plurality of busbars are arranged at predetermined positions in a mold, and then, molten resin filled in the mold is hardened thereby to integrate the busbars into the resin which becomes an insulator part.
In such molding process, the busbars are arranged in the mold by positioning them with fixing pins or the like, before the molten resin is filled into the mold. However, in some cases, positional displacement of the busbars may occur due to arranging error on occasion of positioning or resin pressure of the molten resin, or deformation may occur in the busbar themselves due to the resin pressure, because the busbars are formed of soft material, and it is difficult to take dimensional tolerance. As described, it has sometimes happened that positioning accuracy of the busbars in the mold is deteriorated, and the resin is hardened in a state where the busbars which are arranged in close proximity to each other are electrically contacted with each other.
For this reason, in the obtained busbar integrated type insulator, deterioration of insulating performance and electrifying performance which may cause insulating destruction when electricity is energized and tested are observed. As the results, deterioration in yield of the electric motor is incurred, which has been a factor of increase of the production cost. Moreover, such phenomenon that electrical performance of the busbars integrated type insulator is deteriorated tends to be observed more and more, as the electric motor becomes compact as recently required for use in an automobile or the like.